Related Experiment Video
Updated: Aug 9, 2026
14:12
Dual-Color Fluorescence Cross-Correlation Spectroscopy to Study Protein-Protein Interaction and Protein Dynamics in Live Cells
Published on: December 11, 2021
Phenomenological analysis of observed relations for low-redshift galaxies
1Massachusetts Institute of Technology, Cambridge, Mass. 02139.
Summary
This study estimates the exponent p in the galaxy redshift-distance relation using observational data. Results indicate p is approximately 2, consistent across various analyses and galaxy samples.
Area of Science:
- Cosmology
- Extragalactic Astronomy
- Observational Astrophysics
Background:
- The redshift-distance relation is fundamental for understanding cosmic expansion.
- Previous studies have explored phenomenological models for this relation.
- Accurate estimation of the exponent 'p' is crucial for cosmological parameter determination.
Purpose of the Study:
- To estimate the exponent 'p' in the phenomenological redshift-distance relation z = r(p).
- To analyze galaxy data for 'p' using maximum-likelihood and other statistical methods.
- To investigate the impact of observational biases, such as apparent magnitude cut-offs, on the estimated 'p' value.
Main Methods:
- Maximum-likelihood estimation applied to redshift (z), magnitude (m), and apparent diameter (theta) data.
- Utilized the Reference Catalogue of Bright Galaxies (1964) for a sample of 742 galaxies.
- Employed a generalized Kafka-Schmidt V/V(m) test for independent estimation, accounting for selection effects.
Main Results:
- Maximum-likelihood estimates for 'p' ranged from 1.96 to 2.04 for the full sample (dispersion ~0.08).
- Similar results were obtained for various subsamples, with broader ranges.
- Explicitly accounting for apparent magnitude cut-offs reinforced the finding that p is approximately 2.
- An independent V/V(m) test yielded p = 2.05 for a restricted subsample.
Conclusions:
- The exponent 'p' in the phenomenological redshift-distance relation is robustly estimated to be approximately 2.
- Observational selection effects do not significantly alter this conclusion.
- The findings support models where the redshift-distance relation is consistent with p=2.
Related Concept Videos
02:30Naturalistic Observations
If you want to understand how behavior occurs, one of the best ways to gain information is to simply observe the behavior in its natural context. However, people might change their behavior in unexpected ways if they know they are being observed. How do researchers obtain accurate information when people tend to hide their natural behavior? As an example, imagine that your professor asks everyone in your class to raise their hand if they always wash their hands after using the restroom. Chances...
01:11Observational Studies
Observational studies are a type of analytical study where researchers observe events without any interventions. In other words, the researcher does not influence the response variable or the experiment's outcome.
There are three types of observational studies – Prospective, retrospective, and cross-sectional.
Prospective Study
Prospective studies, also known as longitudinal or cohort studies, are carried out by collecting future data from groups sharing similar characteristics. One example of...
There are three types of observational studies – Prospective, retrospective, and cross-sectional.
Prospective Study
Prospective studies, also known as longitudinal or cohort studies, are carried out by collecting future data from groups sharing similar characteristics. One example of...
01:08Data Collection by Observations
Data collection refers to a systematic way of obtaining, observing, measuring, and analyzing accurate information. Observational studies are one of the most widely used methods of data collection. It involves collecting data by observing the behavior and physical characteristics of a sample without making any modifications to the sample.
An astronomer viewing the motion and brightness of stars in the sky and recording the data is an example of observational data collection. A botanist recording...
An astronomer viewing the motion and brightness of stars in the sky and recording the data is an example of observational data collection. A botanist recording...
01:10Detection of Black Holes
Although black holes were theoretically postulated in the 1920s, they remained outside the domain of observational astronomy until the 1970s.
Their closest cousins are neutron stars, which are composed almost entirely of neutrons packed against each other, making them extremely dense. A neutron star has the same mass as the Sun but its diameter is only a few kilometers. Therefore, the escape velocity from their surface is close to the speed of light.
Not until the 1960s, when the first neutron...
Their closest cousins are neutron stars, which are composed almost entirely of neutrons packed against each other, making them extremely dense. A neutron star has the same mass as the Sun but its diameter is only a few kilometers. Therefore, the escape velocity from their surface is close to the speed of light.
Not until the 1960s, when the first neutron...
01:02¹H NMR: Interpreting Distorted and Overlapping Signals
Spin systems where the difference in chemical shifts of the coupled nuclei is greater than ten times J are called first-order spin systems. These nuclei are weakly coupled, and their chemical shifts and coupling constant can generally be estimated from the well-separated signals in the spectrum.
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are slanted or...
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are slanted or...
01:32UV–Vis Spectroscopy of Conjugated Systems
Organic compounds with conjugated double bonds show strong absorption features in the UV–visible region of the electromagnetic spectrum attributed to π → π* electronic excitations. Generally, a UV–vis absorption spectrum is recorded as a plot of absorbance vs wavelength. The wavelength of maximum absorbance, which manifests as a peak in the absorption spectrum, is denoted as λmax.
One of the factors influencing λmax is the extent of conjugation in the...
One of the factors influencing λmax is the extent of conjugation in the...